Generally, an electric vehicle travels by operating a motor, and is provided with a massive battery unit serving as a power unit for the motor. The battery unit is subject to a temperature rise when it is charged or discharged. When heated above a proper temperature, the battery unit worsens its performance and is quickly aged. Patent Publication No. 3050051 has proposed to introduce cold airstreams from an air conditioning unit of an electric vehicle to a power unit via a duct and to cool a battery unit.